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AR# 7472

*Obsolete* function of CF - dup info

Description

Keywords: 1800, CF, configuration, reset, program, power, ISP

Urgency: Standard

General Description:What is the function of the CF/ pin on the XC18V00 devices?

Solution

1

The CF/ pin allows a soft restart of the FPGA without powering down the FPGA by cycling the PROGRAM/ pin Low. It is controlled through JTAG instruction called CONFIG. See the data sheet for more information.

The following situation is the typical use of this pin. - FPGA is configured and functioning in circuit. - Re-program the 1800 in circuit via JTAG with new bitstream while the FPGA is still functioning. - Execute CONFIG instruction on 1800 device, which will toggle the CF/ pin on the 1800. - FPGA is reset and configured with new bitstream from 1800.

NOTE: The CF/ pin from the 1800 must be connected to the PROGRAM/ pin on the FPGA to take advantage of this feature.

2

The CF/ pin is open drain. It is driven low then released when issued the JTAG CONFIG command. At all other times this pin is tri-stated.